The major concern of this project was twofold: 1) to develop a primate, behavioral model of pain in which the animal's response to noxious stimuli is primarily, if not totally, dependent upon the sensory (intensity) dimension of pain while independent of the affective dimension of pain; 2) to test the hypothesis that narcotic analgesics (viz. morphine) can suppress the sensory (intensity) dimension of noxious heat stimuli. A corollary of this hypothesis that altering the affective state by minor tranquilizers, like diazepam, is not sufficient to suppress the sensory (intensity) dimension of pain was also tested. Techniques employed in this study were application of thermal heat via a contact thermode, using latencies as a behavioral index of perceptual sensitivity, i.m. injections of drugs, and real-time computer control of the experimental sessions. The objectives of this study were to develop a more comprehensive behavioral model of pain in animals (primates) and to broaden our understanding of the analgesic action of narcotics.